Conventional apparatus for feeding bobbin cores to and full bobbins or cops away from a spinning or twisting machine can be comprised of a transport belt extending around the spinning or twisting machine and which is controlled to advance to predetermined positions in succession. The transport belt itself can comprise a support belt and a multiplicity of carriers releasably affixed thereon and formed with pins for transporting the bobbins or cops from the workstations of the machine to a removal position or for transporting the bobbin-winding cores or empty sleeves from a supply position to the workstations of the machine. The pins onto which the bobbins or bobbin cores can be placed can, however, be fixedly connected with the transport belt.
The carriers for the cops and bobbin cores are advantageously disposed alternately on the support belt with a spacing at half the spindle pitch (center-to-center interspindle spacing of the machine). The number of the carriers for the bobbins and the number of carriers for the bobbin cores each correspond to the number of workstations of the respective spinning or twisting machine. Since such machines generally have the same number of workstations along both longitudinal sides of the machine, the carriers as a rule are so disposed upon the support belt that all of the cops can be transferred to the respective cop-receiving carriers in a single operation from the workstations. After the transfer of the cops, the belt can be moved a half spindle pitch so that a carrier with an empty bobbin core or sleeve is disposed at each workstation.
After a transfer of the empty bobbin sleeve to the workstation, the transport belt is displaced until the first carrier bearing a cop is disposed in the removal position. The cops are then individually removed from their carriers in succession with stepped advance of the transport belt by one spindle pitch after another.
Preferably with an offset of one or more of these cycles, the empty bobbin cores are placed upon the respective carriers in the supply position. For the removal of the cops and the mounting of the empty bobbin sleeves to occur in the same cadence, the distance between the removal position and the supply position of the belt must be a whole number of spindle pitches plus one half of a spindle pitch. The spotting of the individual positions of the transport belt is accomplished in the conventional apparatus with a multiplicity of sensors distributed along the length of the machine and which detect markers on the transport belt at these positions and transmit signals to the control unit upon such detection. The control unit can stop the belt drive motor.
It is a drawback with this conventional apparatus that the requirement for a large number of sensors is concomitant to a high capital cost, especially for the cabling necessary for such sensors. The required lengths of the conductors makes the system highly sensitive to stray electromagnetic signals and increases problems with detrimental effects upon the conductor coverings. A further disadvantage is the need for precise adjustment of the sensors for accurate lining up of the carriers. Unnoticed positional changes in the sensors can give rise to a high error frequency and probability.
In German patent DE 40 05 418 C1, an apparatus is disclosed which can be used for automatic doffing and displacing of the bobbins and bobbin cores from the transport belt to the spindles of the workstation of a spinning or twisting machine and wherein, in place of the multiple sensors previously described, a single absolute value signal generator is provided which is juxtaposed with one of the bobbin pins of the belt. The cost of such an absolute value detector is considerable and the reliability leaves much to be desired.
Reference may also be had to German open application DE 41 13 090 A1 which describes a light curtain system which serves only to detect whether a bobbin or sleeve is at a predetermined position. This system provides speed control in dependence upon production speeds and does not detect the absolute position of the belt or provide any indication as to how such a position could be detected or whether such position may be detected.